1. Field of the Invention
The present invention relates to a manufacturing method of an impeller for a fluid transmitting device such as a torque converter or a fluid coupling used in a vehicle or an industrial machine. The present invention relates particularly to an improvement in a manufacturing method of an impeller for a fluid transmitting device, the impeller including an annular, bowl-shaped shell, multiple blades joined to an inner surface of the shell and arranged in a peripheral direction of the shell, and a core having an outer peripheral surface brazed to an intermediate portion of each of the blades so as to couple the intermediate portions of the blades to each other.
2. Description of the Related Art
As described in Japanese Patent Application Laid-open No. 2008-82409, a method has conventionally been known in which the following four steps are performed in the manufacturing of an impeller for such a fluid transmitting device. In the first step, the core is disposed horizontally with a concave inner surface of the core facing up in a state where coupling pieces provided to the blades are fitted in positioning holes provided to the core, respectively. In the second step, a brazing material is disposed on the inner surface of the core. In the third step, the brazing material is melt, and the molten brazing material is caused to penetrate into gaps between the coupling pieces and positioning holes that are fitted to each other and further into gaps between the core and the blades. In the fourth step, the molten brazing material having penetrated into the gaps is solidified.
Such a conventional manufacturing method of an impeller for a fluid transmitting device has the following problem. Specifically, in the third step in which the molten brazing material is caused to penetrate into the gaps between the coupling pieces and positioning holes that are fitted to each other and further into the gaps between the core and the blades, the molten brazing material may flow somewhat unevenly on one side, in the radial direction, of the core since it is difficult to dispose the core strictly horizontally. Thus, while the molten brazing material flows into the gaps between the coupling pieces and the positioning holes, the amount of the molten brazing material adhering unnecessarily to the concave inner surface of the core is not small. Such unnecessary adhesion may lower the yield of the brazing material and further impair the rotational balance of the impeller in some cases.